Autonomous work machine, autonomous work machine control method, and storage medium

ABSTRACT

An autonomous work machine that works in a work area, comprising: a detection unit that detects a plurality of markers arranged to define the work area; a specifying unit that specifies marker information based on a detection result of the detection unit; a setting unit that sets a virtual line connecting the plurality of markers based on the marker information specified by the specifying unit; and a control unit that controls the autonomous work machine such that the autonomous work machine does not deviate to a region beyond the virtual line set by the setting unit.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of International Patent ApplicationNo. PCT/JP2019/028902 filed on Jul. 23, 2019, the entire disclosure ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an autonomous work machine, anautonomous work machine control method, and a storage medium.

Description of the Related Art

PTL 1 discloses that when a marker is recognized, position informationof the marker stored in a robot vehicle is read to grasp a currentposition of the robot vehicle.

CITATION LIST Patent Literature

PTL 1: U.S. Pat. No. 9,497,901

However, in the technique described in PTL 1, it is necessary to preparea plurality of different markers that can be distinguished from eachother, and there is a problem that the procurement cost of the markersincreases.

The present invention has been made in view of the above problem, andthe present invention provides a technique for controlling a workmachine using markers that do not need to be individually distinguished.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided anautonomous work machine according to the present invention is anautonomous work machine that works in a work area and is including adetection unit that detects a plurality of markers arranged to definethe work area, a specifying unit that specifies marker information basedon a detection result of the detection unit, a setting unit that sets avirtual line connecting the plurality of markers based on the markerinformation specified by the specifying unit, and a control unit thatcontrols the autonomous work machine such that the autonomous workmachine does not deviate to a region beyond the virtual line set by thesetting unit.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain principles of theinvention.

FIG. 1 is an external view of a work machine capable of autonomouslytraveling according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the work machine according to anembodiment of the present invention as viewed from the side.

FIG. 3 is a diagram illustrating a configuration example of a controlsystem according to an embodiment of the present invention.

FIG. 4A is an explanatory diagram of a method for setting a virtual lineand a method for determining adjacent markers according to an embodimentof the present invention.

FIG. 4B is an explanatory diagram of a method for determining adjacentmarkers according to an embodiment of the present invention.

FIG. 4C is an explanatory diagram of a method for determining adjacentmarkers according to an embodiment of the present invention.

FIG. 4D is an explanatory diagram of a method for determining adjacentmarkers according to an embodiment of the present invention.

FIG. 4E is an explanatory diagram of a method for determining adjacentmarkers according to an embodiment of the present invention.

FIG. 4F is an explanatory diagram of a method for determining adjacentmarkers according to an embodiment of the present invention.

FIG. 4G is an explanatory diagram of a method for determining adjacentmarkers according to an embodiment of the present invention.

FIG. 5A is a flowchart illustrating a procedure of processing performedby an autonomous work machine according to a first embodiment.

FIG. 5B is a flowchart illustrating a procedure of processing performedby the autonomous work machine according to the first embodiment.

FIG. 6 is an explanatory diagram of how to obtain a distance to avirtual line according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of a captured imageaccording to an embodiment of the present invention.

FIG. 8A is a flowchart illustrating a procedure of processing performedby an autonomous work machine according to a second embodiment.

FIG. 8B is a flowchart illustrating a procedure of processing performedby the autonomous work machine according to the second embodiment.

FIG. 9 is a diagram illustrating an example of map information obtainedby plotting marker positions according to a third embodiment.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. Note that the same componentsare denoted by the same reference numerals throughout the drawings.

First Embodiment

FIG. 1 is an external view of an autonomous work machine capable ofautonomously traveling according to an embodiment of the presentinvention. Hereinafter, a moving direction (vehicle length direction), alateral direction (vehicle width direction) orthogonal to the movingdirection, and a vertical direction orthogonal to the moving directionand the lateral direction in a side view of the autonomous work machineare respectively defined as a front-and-rear direction, a left-and-rightdirection, and an up-and-down direction, and the configuration of eachpart will be described in accordance with the above definition.

<Configuration of Autonomous Work Machine>

In FIG. 1, reference numeral 10 denotes an autonomous work machine(hereinafter referred to as a “work vehicle”). Specifically, the workvehicle 10 functions as a lawn mower that autonomously travels. However,the lawn mower is merely an example, and the present invention is alsoapplicable to other types of work machines. The work vehicle 10 includesa camera unit 11 including a plurality of cameras (a first camera 11 aand a second camera 11 b), and calculates and acquires distanceinformation between an object existing forward and the work vehicle 10using images captured by the first camera 11 a and the second camera 11b having parallax. Then, the operation of the work vehicle 10 iscontrolled based on the captured image and the object recognition modelheld in advance.

FIG. 2 is a diagram illustrating the work vehicle 10 observed in thelateral direction (vehicle width direction). As illustrated in FIG. 2,the work vehicle 10 includes the camera unit 11, a vehicle body 12, astay 13, front wheels 14, rear wheels 16, a blade 20, a work motor 22, amotor holding member 23, a blade-height adjustment motor 100, and atranslation mechanism 101. The work vehicle 10 further includes a travelmotor 26, a group of various sensors S, an electronic control unit (ECU)44, a charging unit 30, a battery 32, a charging terminal 34, and acommunication unit 35.

The vehicle body 12 of the work vehicle 10 includes a chassis 12 a, anda frame 12 b attached to the chassis 12 a. The front wheels 14 includeone left wheel and one right wheel each having a smaller diameter andfixed to the front of the chassis 12 a through the stay 13 in thefront-and-rear direction. The rear wheels 16 include one left wheel andone right wheel each having a larger diameter and attached to the rearof the chassis 12 a.

The blade 20 is a rotary blade for a lawn mowing work, and is attachednear the central position of the chassis 12 a. The work motor 22 is anelectric motor disposed above the blade 20. The blade 20 is connectedwith the work motor 22, and is rotatably driven by the work motor 22.The motor holding member 23 holds the work motor 22. The motor holdingmember 23 is restricted in rotation with respect to the chassis 12 a,and is allowed to move in the up-and-down direction by, for example, thecombination of a guide rail and a slider movable up and down while beingguided by the guide rail.

The blade-height adjustment motor 100 is a motor for adjusting theheight in the up-and-down direction of the blade 20 to the groundsurface GR. The translation mechanism 101 is connected to theblade-height adjustment motor 100, and is a mechanism for convertingrotation of the blade-height adjustment motor 100 into translation inthe up-and-down direction. The translation mechanism 101 is alsoconnected with the motor holding member 23 that holds the work motor 22.

The rotation of the blade-height adjustment motor 100 is converted intothe translation (movement in the up-and-down direction) by thetranslation mechanism 101, and the translation is transmitted to themotor holding member 23. Due to the translation (movement in theup-and-down direction) of the motor holding member 23, the work motor 22held by the motor holding member 23 also is translated (moves in theup-and-down direction). Due to the movement in the up-and-down directionof the work motor 22, the height of the blade 20 with respect to theground surface GR is adjustable.

The travel motor 26 is two electric motors (prime movers) attached tothe chassis 12 a of the work vehicle 10. The two electric motors areconnected one-to-one to the left and right rear wheels 16. Byindependently rotating the left and right wheels forward (rotating inthe forward direction) or backward (rotating in the backward direction)with the front wheels 14 as driven wheels and the rear wheels 16 asdriving wheels, the work vehicle 10 can be moved in various directions.

The charging terminal 34 is a charging terminal provided at a front endposition in the front-and-rear direction of the frame 12 b, and isconnected with a corresponding terminal of a charging station (forexample, a charging station 300 that will be described later withreference to FIG. 3) to receive electric power supplied from thecharging station. The charging terminal 34 is connected with thecharging unit 30 through wiring, and the charging unit 30 is connectedwith the battery 32. In addition, the work motor 22, the travel motor26, and the blade-height adjustment motor 100 are connected to thebattery 32, and are supplied with power from the battery 32.

An ECU 44 is an electronic control unit including a microcomputer formedon a circuit board and controls the operation of the work vehicle 10.The details of the ECU 44 will be described later. The communicationunit 35 can transmit and receive information to and from an externaldevice (for example, a charging station that will be described later, acommunication terminal possessed by a user, a remote controller foroperating the work vehicle 10, or the like) connected with the workvehicle 10 in a wired or wireless manner.

FIG. 3 is a diagram illustrating a configuration example of a controlsystem according to an embodiment of the present invention. A controlsystem 1 includes the work vehicle 10 and the charging station 300. Notethat a remote controller for operating a communication terminalpossessed by a user that will be described later or the work vehicle 10may be further included.

As illustrated in FIG. 3, the ECU 44 included in the work vehicle 10includes a CPU 44 a, an I/O 44 b, and a memory 44 c. The I/O 44 b inputsand outputs various types of information. The memory 44 c is a read-onlymemory (ROM), an electrically erasable programmable read-only memory(EEPROM), a random access memory (RAM), or the like. The memory 44 cstores a captured image, a work schedule of the work vehicle 10, mapinformation on a work area, various programs for controlling theoperation of the work vehicle 10, and the like. In order to operate eachprocessing unit for achieving the present invention, the ECU 44 readsand executes a program stored in the memory 44 c.

The ECU 44 is connected with the group of various sensors S. The sensorgroup S includes an orientation sensor 46, a GPS sensor 48, a wheelspeed sensor 50, an angular speed sensor 52, an acceleration sensor 54,a current sensor 62, and a blade height sensor 64.

The orientation sensor 46 and the GPS sensor 48 are sensors foracquiring information on the orientation and position of the workvehicle 10. The orientation sensor 46 detects the orientation inaccordance with terrestrial magnetism. The GPS sensor 48 receives aradio wave from a GPS satellite and detects information indicating acurrent position (latitude and longitude) of the work vehicle 10. To benoted, in addition to or instead of the GPS sensor 48 and theorientation sensor 46, odometry and an inertial measurement unit (IMU)may be provided.

The wheel speed sensor 50, the angular speed sensor 52, and theacceleration sensor 54 are sensors for acquiring information regarding amoving state of the work vehicle 10. The wheel speed sensor 50 detectsthe wheel speeds of the left and right rear wheels 16. The angular speedsensor 52 detects an angular speed around an axis in the up-and-downdirection (z axis in the vertical direction) of the gravity centerposition of the work vehicle 10. The acceleration sensor 54 detectsaccelerations in the 3 orthogonally triaxial directions of x, y, and zaxes acting on the autonomous work vehicle 10.

The current sensor 62 detects the current consumption (amount of powerconsumption) of the battery 32. The detection result of the currentconsumption (amount of power consumption) is stored in the memory 44 cof the ECU 44. In a case where a predetermined amount of power isconsumed and the amount of power stored in the battery 32 becomes notmore than a threshold, the ECU 44 performs returning control for causingthe autonomous work vehicle 10 to return to the charging station 300 forcharging. Note that a daily work schedule may be stored in the memory 44c, and the returning control may be performed in response to completionof work to be performed on that day.

The blade height sensor 64 detects a height of the blade 20 with respectto a ground surface GR. The detection result of the blade height sensor64 is output to the ECU 44. On the basis of the control of the ECU 44,the blade-height adjustment motor 100 is driven and the blade 20 movesup and down in the up-and-down direction to adjust the height from theground surface GR.

Outputs from the group of various sensors S are input into the ECU 44through the I/O 44 b. On the basis of the outputs of the group ofvarious sensors S, the ECU 44 supplies power from the battery 32 to thetravel motor 26, the work motor 22, and the height adjustment motor 100.The ECU 44 controls the traveling of the work vehicle 10 by outputting acontrol value via the I/O 44 b and controlling the travel motor 26. Inaddition, the height of the blade 20 is adjusted by outputting a controlvalue through the I/O 44 b and controlling the height adjustment motor100. Further, the rotation of the blade 20 is controlled by outputting acontrol value through the I/O 44 b to control the work motor 22. Here,the I/O 44 b can function as a communication interface and can beconnected to another device in a wired or wireless manner via a network150.

The charging station 300 functions as a charging device for charging abattery (battery 32) of the work vehicle 10. The work vehicle 10 isinstalled in the work area, and can return to the charging station 300and perform charging by connecting the charging terminal 34 to thecharging station 300.

<Virtual Line Setting Method>

A virtual line setting method according to the present embodiment willbe described with reference to FIG. 4A. A virtual line is an imaginaryline connecting markers arranged to define the work area. In FIG. 4A,reference numeral 400 denotes a region (for example, the entire siteowned by a user) including the work area (for example, a garden) wherethe work vehicle 10 performs work. Reference numerals 401 a to 401 ndenote markers according to the present embodiment. An area surroundedby these markers 401 a to 401 n is a work area. The work vehicle 10performs work so as not to deviate from this work area by performingcontrol so as not to deviate to a region beyond the virtual line. Notethat the work area may be defined by partitioning the entire site usingan existing area wire of a type that is embedded in the ground, anddisposing markers in a part of the site to provide a non-entry area.That is, the present invention can also be applied to a case where awork area is defined by combining an existing area wire and a marker.

Reference numeral 402 denotes a traveling direction of the work vehicle10, and reference numeral 403 denotes a range (for example, an angle ofview range) that the work vehicle 10 can recognize by the camera unit11. In the illustrated example, four markers 401 a to 401 d are includedin the recognizable range. When recognizing the marker, the work vehicle10 sets a virtual line (virtual wire) between two adjacent markers. Inthe illustrated example, a virtual line 411 is set between the marker401 a and the marker 401 b, a virtual line 412 is set between the marker401 b and the marker 401 c, and a virtual line 413 is set between themarker 401 c and the marker 401 d. To be noted, for example, since themarker 401 b and the marker 401 d are not adjacent markers, a virtualline is not set.

Here, the virtual line is not limited to a straight line. For example, asmooth curve may be set like a virtual line 431 set between the marker401 i and the marker 401 j.

<Adjacent Marker Determination Method 1: Distance between Markers>

Whether two markers are adjacent markers can be determined based on thedistance between the markers in the case where it is assumed that themarkers are arranged at predetermined distance intervals. When thedistance between the markers is within a predetermined distance range(for example, 2.5 m to 3.5 m), it may be determined that the markers areadjacent markers, and when the distance is out of the predetermineddistance range, it may be determined that the markers are not adjacentmarkers. In FIG. 4A, since the length (for example, 4 m) of a line 414is out of the predetermined distance range, the line is not set as avirtual line. As a result, it is possible to prevent the work from notbeing performed in the region of a triangle obtained by connecting themarker 401 b, the marker 401 c, and the marker 401 d.

As described above, according to the determination method 1, among theplurality of markers, two markers whose distance between the markers iswithin the predetermined distance range are specified as adjacentmarkers. The predetermined distance range do not have to have an upperlimit value or a lower limit value, for example, like 2.5 m or more, 3 mor more, 3 m or less, or 3.5 m or less.

<Adjacent Marker Determination Method 2: Use of Indicator>

To be noted, the method for determining whether two markers are adjacentmarkers is not limited to a method using the distance between themarkers. For example, by using a marker, such as the marker 401 m inFIG. 4A, including an indicator (For example, 431 and 432) forindicating a direction in which an adjacent marker is present, eachindicator may be detected, and a nearby marker present in the directionindicated by the indicator 431 or 432 may be determined to be anadjacent marker. In the illustrated example, a virtual line 421 is setbetween the marker 401 l and the marker 401 m existing in the directionindicated by the indicator 431, and a virtual line 422 is set betweenthe marker 401 n and the marker 401 n. In this case, each marker may beconfigured to include indicators indicating at least two directionssimilarly to 401 m.

As described above, according to the determination method 2, each markerincludes an indicator indicating the direction in which an adjacentmarker exists, and a second marker existing in the direction indicatedby the indicator of a first marker can be specified as an adjacentmarker. When there are a plurality of markers in the direction indicatedby the indicator of the first marker, the marker existing closest to thefirst marker may be specified as the adjacent marker. In addition, incombination with the determination method 1, a marker in a directionindicated by the indicator and within a predetermined distance range(for example, 2.5 m to 3.5 m) may be specified as an adjacent marker. Inaddition, the direction indicated by the indicator may be freely changedby the user. For example, the direction of the indicator may beadjustable using a rotation mechanism or the like.

<Adjacent Marker Determination Method 3: Detecting Marker Behind>

In the case of the determination method 1, in the case where threemarkers are arranged in an equilateral triangle shape at intervals of apredetermined distance (for example, 3 m), or in the case where fourmarkers are arranged in a square shape at intervals of a predetermineddistance (for example, 3 m), there is a possibility that it is notpossible to enter a region inside the equilateral triangle or thesquare, and work cannot be performed in these regions.

Here, FIG. 4B is an explanatory diagram of a method of determining anadjacent marker in a work area in which an equilateral triangular orsquare region is formed. Reference numeral 450 denotes a region (forexample, the entire site owned by a user) including the work area (forexample, a garden) where the work vehicle 10 performs work. Referencenumerals 451 a to 451 p denote markers according to the presentembodiment. An area surrounded by these markers 451 a to 451 p is a workarea. The work vehicle 10 performs work so as not to deviate from thework area.

The markers 451 a to 451 p are arranged at predetermined distance (forexample, 3 m) intervals. In this work area, an equilateral triangularregion is formed by three markers of the marker 451 b, the marker 451 c,and the marker 451 d. Similarly, a square region is formed by fourmarkers of the marker 4511, the marker 451 m, the marker 451 n, and themarker 451 o. If there are such regions, when the determination method 1is used, the work vehicle 10 cannot move to a region behind the virtualline connecting the marker 451 b and the marker 451 c and the virtualline connecting the marker 451 l and the marker 451 o, so that the workcannot be performed in these regions.

Therefore, when another marker is detected behind the two markers, itmay be determined that the two markers are not adjacent markers. In theillustrated example, two markers of the marker 451 b and the marker 451d are detected, and the other marker 451 c is further detected behindthe two markers. Therefore, it is determined that the two markers 451 band 451 d are not adjacent markers. Similarly, two markers of the marker451 l and the marker 451 o are detected, and the other markers 451 m and451 n are further detected behind the two markers. Therefore, it isdetermined that the two markers 451 l and 451 o are not adjacentmarkers.

As a result, no virtual line is set between the marker 451 b and themarker 451 c and between the marker 451 l and the marker 451 o, so thatthe work vehicle 10 can enter an equilateral triangular area and asquare area to perform work.

As described above, according to the determination method 3, whenanother marker is present in a region behind a line connecting twomarkers, it is specified that the two markers are not adjacent markers.However, when the determination method 3 is applied, in the case whereanother marker at a position far away from the two markers is detected,there is a possibility of erroneous entry to the back region. Therefore,a configuration in which movement to the back region is only possiblewhen the distance to the other marker is calculated and the calculateddistance is equal to or less than a predetermined distance (for example,4 m), or when it is determined that the other marker is a markeradjacent to either one of the two markers on the front side. As aresult, it is possible to suppress entry into a region that should notbe originally entered.

<Adjacent Marker Determination Method 4: Tracing Markers in Advance>

FIG. 4C is an explanatory diagram of an example of a method ofdetermining adjacent markers. Reference numeral 460 denotes a region(for example, the entire site owned by a user) including the work area(for example, a garden) where the work vehicle 10 performs work.Reference numerals 461 a to 461 m denote markers according to thepresent embodiment. An area surrounded by these markers 461 a to 461 mis a work area. The work vehicle 10 performs work so as not to deviatefrom the work area.

Before starting work by the work vehicle 10, a user 462 directlycontrols the work vehicle 10 by operating a remote controller 463, andmoves the work vehicle 10 one lap along each marker. An operation signalfrom the remote controller 463 is received via the communication unit 35of the work vehicle 10.

In addition, the work vehicle 10 includes a GPS sensor 48, and stores atrajectory obtained by sequentially tracing each marker according to theoperation signal of the remote controller 463 as trajectory informationof the work area. As a result, since the trajectory information of thework area can be grasped before the start of the work, it is possible todetermine whether or not the two markers are adjacent markers, bydetermining that markers not following the trajectory are not adjacentmarkers after the start of the work.

As described above, according to the determination method 4, thetrajectory information of the work vehicle 10 is acquired by causing thework vehicle 10 to travel along each of the arranged markers. As aresult, two markers matching the trajectory information among theplurality of markers can be specified as adjacent markers.

<Adjacent Marker Determination Method 5: Drawing Work Area Boundary onMap by Communication Terminal>

FIG. 4D is a diagram illustrating an example of drawing something on amap related to a work area displayed on a communication terminal held bya user. Reference numeral 470 denotes a communication terminal of theuser, which is, for example, a tablet or a smartphone. Reference numeral471 denotes a hand of the user. Reference numeral 472 represents mapinformation on the work area displayed on a display screen of thecommunication terminal 470. In the illustrated example, a map of a siteincluding a home and a garden of the user as viewed from above isdisplayed. Reference numeral 473 denotes a roof of the user's home, andreference numeral 474 denotes a tree space in a site of the user's home.Here, FIG. 4E is an external view of a part of the site including theuser's home corresponding to the map information of FIG. 4D.

In FIG. 4D, reference numeral 475 denotes a boundary traced on the mapby the user using a finger of the hand 471. Similarly, reference numeral476 indicates a boundary traced around the tree space by the user usingthe finger of hand 471. A tree spaces 474 is an island excluded from thework area. Note that the boundary may be designated by connectingpositions pointed by a finger instead of tracing using the finger.

In this manner, the boundary of the work area is designated on a mapdisplayed on the communication terminal 470, and the designated boundaryinformation (information indicating the position of a boundary line) istransmitted to the work vehicle 10. As a result, since the work vehicle10 can acquire the boundary information designated by the useroperation, the work vehicle 10 can recognize its self-position andorientation using the GPS sensor 48 and the orientation sensor 46, anddetermine whether or not two detected markers are adjacent markers usingthe self-position and orientation and the boundary information. In theexample of FIG. 4E, the work vehicle 10 can determine that a marker 481and a marker 482 are not adjacent markers from the acquired boundaryinformation. To be noted, the self-position and orientation may berecognized by using, in addition to or instead of the GPS sensor 48 andthe orientation sensor 46, an odometry and an inertial measurement unit(IMU).

To be noted, the method of tracing the boundary is not limited to themethod in which the user traces the boundary using the finger of thehand 471. As indicated by black circles 477 in FIG. 4D, the user maysequentially point out a plurality of positions of markers on the mapalong the boundary using the finger of the hand 471 to acquire markerarrangement information as the boundary information. The boundaryinformation may be transmitted from the communication terminal 471 tothe work vehicle 10.

Even in a case where the position of each marker is pointed out, it ispossible to determine whether or not two detected markers are adjacentmarkers by using the self-position and orientation and the boundaryinformation (marker arrangement information). For example, in theexample of FIG. 4E, the work vehicle 10 can determine that the marker481 and the marker 482 are not adjacent markers from the boundaryinformation (marker arrangement information).

As described above, according to the determination method 5, theboundary information (for example, arrangement information of aplurality of markers arranged at the boundary of the work area (positioninformation designated by pointing) or information of a boundary line(line traced with a finger) indicating the boundary of the work area) ofthe work area designated on the map including the work area is acquired.As a result, two markers matching the boundary information among theplurality of markers can be specified as adjacent markers.

<Adjacent Marker Determination Method 6: Enclosing Island with DifferentTypes of Markers>

FIG. 4F illustrates an example of a method using two types of markers.Different types (For example, different colors, different shapes, andthe like) of markers are respectively used for each marker arranged onthe boundary of the work area and each marker arranged around the treespace 474 which is an island excluded from the work area. As a result,the work vehicle 10 can discriminate different types of markers from thefeatures of the markers extracted from the captured image, and the workvehicle 10 can determine that a marker 483 and a marker 484 are notadjacent markers from the captured image.

Note that the marker is not limited to two types of markers, and in acase where there are a plurality of islands, different types of markersmay be used for respective islands. Therefore, the present invention isalso applicable to a case where three or more types of markers are used.

In this manner, a plurality of first type markers defining the outeredge of the work area and a plurality of second type markers definingthe internal region (island) enclosed by the outer edge and excludedfrom the work area are used. This allows the first type markers and thesecond type markers to be identified as not being adjacent markers.

<Adjacent Marker Determination Method 7: Using Different Types ofMarkers for Respective Distances>

FIG. 4G is a diagram illustrating an example in which markers arearranged at short intervals in a region having a complicated shape.Reference numerals 491 a to 491 e each denote a marker for a firstdistance (for example, 3 m) interval. Reference numerals 492 a to 492 feach denote a marker for a second distance (for example, 1 m) interval.The first type markers for the first distance interval and the secondtype markers for the second distance interval are different types ofmarkers having, for example, different colors, shapes, sizes, or thelike.

In the illustrated example, the marker 491 b, the marker 491 c, and themarker 491 d form an equilateral triangle shape, and the marker 491 c,the marker 491 d, and the marker 491 e also form an equilateral triangleshape. A case where only the markers 491 a to 491 e are arranged in sucha complicated shape will be considered. If it is determined that twomarkers are not adjacent markers when another marker is detected behindthe two markers as in the determination method 3, for example, in thecase where the work vehicle is traveling toward a position between themarker 491 c and the marker 491 d, the marker 491 e is detected at theback, so that the work vehicle can travel in a direction approaching themarker 491 e at the back beyond the boundary of the work area connectingthe marker 491 c and the marker 491 d.

Therefore, the markers 492 a to 492 f are further arranged at placeshaving complicated shapes. Accordingly, since the work vehicle 10further detects the marker 492 c and the marker 492 d on the lineconnecting the marker 491 c and the marker 491 d, it is possible todetermine that the two markers (the marker 491 c and the marker 491 d)are adjacent markers. Therefore, it is possible to prevent the workvehicle 10 from deviating to the back region beyond the boundary of thework area connecting the marker 491 c and the marker 491 d. To be noted,although a case where the two markers 492 c and 492 d are detected ishas been described for the illustrated example, it may be determinedthat the two markers (the marker 491 c and the marker 491 d) areadjacent markers when either the marker 492 c or the marker 492 d isdetected on the line connecting the marker 491 c and the marker 491 d.

As described above, according to the determination method 7, theplurality of first type markers arranged at the first distance intervalsand the plurality of second type markers arranged at the second distanceintervals shorter than the first distance intervals are used.Accordingly, when one or more second type markers are present betweentwo first type markers among a plurality of first type markers, the twofirst type markers can be identified as adjacent markers.

<Processing>

Next, a procedure of processing performed by the work vehicle 10according to the present embodiment will be described with reference toflowcharts of FIGS. 5A and 5B. The work vehicle 10 according to thepresent embodiment sets a virtual line between markers and performscontrol so that the work vehicle 10 does not deviate to a region beyondthe virtual line.

In step S501, the CPU 44 a acquires a stereo image captured by thecamera unit 11.

In step S502, the CPU 44 a acquires a distance image based on the stereoimage.

In step S503, the CPU 44 a trims an image of one of the first camera 11a and the second camera 11 b constituting the camera unit 11. In thepresent embodiment, an image of the second camera 11 b is used.

In step S504, the CPU 44 a executes object recognition processing usingthe trimmed image. Features of objects including persons and markers arelearned in advance by machine learning, and an object is recognized bycomparison with the learning result.

In step S505, the CPU 44 a determines whether or not a marker has beenrecognized as a result of the object recognition processing in stepS504. In the case where it is determined that a marker has beenrecognized, the process proceeds to step S506. In the case where it isdetermined that a marker has not been recognized, the process proceedsto step S517.

In step S506, the CPU 44 a acquires the gravity center position of themarker in the image. For example, a specific position of the marker isspecified as the gravity center position based on information of thegravity center position of the marker held in advance. Note that thegravity center position is merely an example, and is not limited to thegravity center position. The position may be a top position of themarker, or may be a ground contact position where the marker and theground are in contact with each other.

In step S507, the CPU 44 a acquires information of the distance from thework vehicle 10 to the gravity center position of the marker as markerinformation using the distance image acquired in step S502.

In step S508, the CPU 44 a determines whether or not a plurality ofmarkers have been recognized in step S505. In the case where it isdetermined that a plurality of markers have been recognized, the processproceeds to step S509. In the case where only a single marker has beenrecognized, the process proceeds to step S515.

In step S509, the CPU 44 a determines whether or not two markersincluded in the plurality of markers are adjacent markers. In thepresent embodiment, whether or not the distance between the two markersis within a predetermined distance range is determined, and when thedistance is within the predetermined distance range, it is determinedthat the markers are adjacent markers. In the present embodiment, it isassumed that the markers are installed at intervals of 3 m, but themarkers are not necessarily arranged at equal intervals of 3 m, andthere is a possibility that some deviation occurs. Therefore, it isdetermined that the markers are adjacent markers if the markers arewithin the predetermined distance range, for example, in a range of 2.5m to 3.5 m. In the case where it is determined that the markers areadjacent markers, the process proceeds to step S510. In contrast, in thecase where it is determined that the markers are not adjacent markers,the process proceeds to step S511. As a method of determining whether ornot the markers are adjacent markers, other determination methodsdescribed with reference to FIGS. 4A to 4G may be used.

In step S510, the CPU 44 a sets a virtual line between the two markersdetermined to be adjacent markers.

In step S511, the CPU 44 a determines whether or not the determinationhas been completed for all combinations of two markers among theplurality of markers. When the determination is completed for all thecombinations, the process proceeds to step S512. In contrast, in thecase where there remains a combination for which the determination hasnot been performed yet, the process returns to step S509, and thedetermination is performed on a new combination of two markers.

In step S512, the CPU 44 a calculates the distance from the work vehicle10 to a virtual line located ahead of the work vehicle 10 in thetraveling direction based on the traveling direction of the work vehicle10 and the virtual line located ahead in the traveling direction. In theexample of FIG. 4A, the distance to an intersection with the virtualline 411 located ahead in the traveling direction 402 is calculated.

Here, an example of a method of calculating the distance to theintersection with the virtual line 411 located ahead in the travelingdirection 402 will be described with reference to FIG. 6. In FIG. 6, apoint O is a current position of the work vehicle 10. A point Acorresponds to the marker 401 a in FIG. 4A, and a point B corresponds tothe marker 401 b in FIG. 4A. When the distance to be obtained is X, X isthe length of a line OC. Here, the length of a line OA and the length ofa line OB can be obtained from the distance image. Furthermore, an angleα and an angle β can also be obtained from the imaging direction(normally, the same direction as the traveling direction 402) and theviewing angle of the camera unit 11, and the directions of the point Aand the point B. Then, a perpendicular line is drawn down from the pointA to the line OC, and an intersection thereof is defined as D.Similarly, a perpendicular line is drawn down from the point B to anextension line of the line OC, and an intersection thereof is defined asE. At this time, since a triangle ACD and a triangle BCE are similar,AD:BE=CD:CE holds. Then, as illustrated in FIG. 7 illustrating anexample of the captured image, the ratio between AD and BE can beobtained from the ratio of the distance from a center line 701 of theimage of one camera captured by the camera unit 11 (that is, the ratioof the length between AG and BH).

In FIG. 6, AD=OAsinα, BE=OBsinβ, CD=OC—OAcosα, and CE=OBcosβ-OC hold,and therefore a distance X to the point C can be obtained by

AD:BE = CD:CE ↔ O A  sin   α:O B sin  β = O C − O A cos   α:O B cos  β − O C ↔ O C = O A O B × (sin αcos β + cos  α sin  β)/(OBsin β + O A sin  α) = O A O B sin (α + β)/(OBsin β + O A sin  α) = X

In step S513, the CPU 44 a determines whether or not the distance fromthe work vehicle 10 to the virtual line located ahead of the workvehicle 10 in the traveling direction is equal to or less than athreshold value (for example, 0.1 m). When it is determined that thedistance is equal to or less than the threshold, the process proceeds toS514. In contrast, in the case where the distance is larger than thethreshold value, the process proceeds to step S517.

In step S514, the CPU 44 a executes an avoidance operation based on thevirtual line. Specifically, when the work vehicle 10 approaches athreshold (for example, 0.1 m) from the virtual line, the work vehicle10 stops, moves backward, or turns. Accordingly, it is possible toprevent the work vehicle 10 from deviating to a region beyond thevirtual line. For example, the work vehicle 10 stops, moves backward, orturns the work vehicle 10 when the distance from the work vehicle 10 tothe virtual line 415 becomes equal to or less than the threshold so asnot to deviate to the back region beyond the intersection position ofthe line 415 extending in the traveling direction 415 and the virtualline 411 existing in the traveling direction 415 illustrated in FIG. 4A.As a result, the work vehicle 10 can perform work without deviating fromthe work area. Here, the turning is to change the traveling direction ofthe work vehicle 10, and includes moving along a parabolic trajectorywhen the site is viewed from above, rotating on the spot after stoppingat a certain point to change the traveling direction, and going aroundso as not to enter the region defined by the virtual line.

When the distance to the virtual line becomes equal to or less thananother threshold value (for example, 1.5 m), control for lowering thetraveling speed of the work vehicle 10 heading for the virtual line 415may be further performed. By decelerating in advance before performingan avoidance operation such as stop, backward movement, or turning, itis possible to suppress sudden operation such as sudden stop, suddenbackward movement after sudden stop, or sudden turning.

In step S515, the CPU 44 a determines whether or not the distance fromthe work vehicle 10 to the marker is equal to or less than a threshold.The threshold here is, for example, 0.5 m, but is not limited to thisvalue. When it is determined that the distance is equal to or less thanthe threshold, the process proceeds to S516. In contrast, in the casewhere the distance is larger than the threshold value, the processproceeds to step S517.

In step S516, the CPU 44 a executes the avoidance operation.Specifically, when the work vehicle 10 stops, moves backward, or turnswhen reaching a threshold distance (for example, 0.5 m) from a marker.Since only one marker is detected, the avoidance operation is performedindependently of the virtual line. Thereafter, the process proceeds tostep S517.

In step S517, the CPU 44 a determines whether to end the series ofprocessing. For example, there are a case where the remaining batterycharge becomes equal to or lower than a threshold and it is necessary toreturn to the charging station 300, a case where a predetermined timehas elapsed from the start of work, and a case where work in the workarea has been completed (for example, the lawn in the work area has beenmowed). This also applies to a case where the user operates the powersource of the work vehicle 10 to be turned off. In the case where it isdetermined not to end the series of processing, the process returns tostep S501. In contrast, in the case where it is determined to end theseries of processing, the processing of FIGS. 5A and 5B is ended.

As described above, in the present embodiment, two markers are detected,and a virtual line is set between the markers. Then, the avoidanceoperation is executed so that the work vehicle does not deviate to theback region beyond the virtual line. As a result, it is possible tocontrol the work machine using the same type of marker, and it is notnecessary to prepare a plurality of markers having different features sothat each of the markers can be distinguished. Therefore, it is alsopossible to reduce the introduction cost of the marker. In addition, inorder to set the virtual line (virtual wire), it is not necessary toprovide an area wire (for example, a wire embedded in the ground) fordefining the work area, so that the cost can be reduced. To be noted, asdescribed above, an existing area wire and a marker may be combined todefine the work area, and in this case, the area wire does not have tobe provided for some regions, so that the cost can be reduced. Further,since the markers can be freely arranged, the shape of the work area canbe flexibly changed. For example, in the case where the userhimself/herself works in a part of a garden, there is a case where thework vehicle is not desired to enter the area. In this case, by definingthe region so as to be surrounded by markers, it is possible to easilycreate an area where the work vehicle does not temporarily enter.

[Modifications]

To be noted, when it is necessary to return to the charging station 300or when it is necessary to move to a predetermined position, the CPU 44a sets a travel route for the work vehicle 10 to travel according to theset travel route. At that time, the travel route is set such that thevirtual line does not exist on the travel route. Accordingly, it ispossible to prevent traveling beyond the virtual line and deviating.

In addition, although an example in which the processing is performed inconsideration of combinations of two markers for all the detectedmarkers has been described in step S511, markers on the left and rightof the line along the traveling direction may be set as processingtargets based on the traveling direction of the work vehicle 10. Forexample, in the example of FIG. 4A, it is possible to set only markerson the left and right of the line 415 along the traveling direction 415instead of processing all the combinations (6 combinations) of the fourmarkers 401 a to 401 d. In this case, three combinations of the marker401 a and the marker 401 b, the marker 401 a and the marker 401 c, andthe marker 401 a and the marker 401 d may be set as processing targets,and three combinations of the marker 401 b and the marker 401 c, themarker 401 b and the marker 401 d, and the marker 401 c and the marker401 d may be excluded from the processing targets. This makes itpossible to speed up the processing.

In addition, in the present embodiment, an example has been described inwhich, when the distance from the work vehicle 10 to the virtual line islarger than the threshold in step S513, the process returns to step S501through step S517, and the stereo image is acquired again. However, inthe case re-capturing images all the time, as the work vehicle 10travels and approaches the virtual line, a plurality of markers may cometo not be detected. Therefore, instead of necessarily returning to stepS501 and re-capturing images, control may be performed such that thetiming at which the distance from the work vehicle 10 to the virtualline becomes equal to or less than the threshold is estimated on thebasis of the traveling speed of the work vehicle 10, and the avoidanceoperation is executed when that timing arrives. Alternatively, adistance from a certain point to the virtual line is calculated, andthereafter, a moving distance from the point is constantly measured byodometry, an inertial measurement unit (IMU), or the like. Then, theoperation of the work vehicle 10 may be controlled based on thecalculated distance and the moving distance being measured. For example,the avoidance operation may be executed in response to the movingdistance being measured reaching the “distance from the point to thevirtual line”.

In addition, in steps S512 and S513, an example in which the avoidanceoperation is controlled on the basis of the distance between the workvehicle 10 and the virtual line has been described, but it is notlimited to the distance. For example, a time required for the workvehicle 10 to reach the virtual line 411 may be calculated, and whetheror not the work vehicle 10 has reached the virtual line may bedetermined on the basis of the calculated time. For example, the timemay be calculated based on the traveling speed of the work vehicle 10and the distance from the work vehicle 10 to the virtual line 411. Then,the avoidance operation may be controlled to be executed when thedifference between the time and the elapsed time is equal to or lessthan a threshold. Similarly, in step S515, an example in which theavoidance operation is controlled on the basis of the distance betweenthe work vehicle 10 and a marker has been described, but it is notlimited to the distance. For example, a time required for the workvehicle 10 to reach the marker may be calculated, and whether or not thework vehicle 10 has reached the marker may be determined on the basis ofthe calculated time.

In addition, control may be performed in parallel with repeating theprocessing by returning to step S501, such that the avoidance operationis separately executed when the timing at which the distance from thework vehicle 10 to the virtual line becomes equal to or less than thethreshold arrives.

Second Embodiment

In the first embodiment, an example has been described in whichinformation of the distance to a detected marker is acquired as markerinformation, and the avoidance operation is performed by calculating thedistance from the work vehicle to the virtual line and the time untilthe work vehicle reaches the virtual line are calculated using thedistance information. In contrast, in a second embodiment, an examplewill be described in which marker position information indicatingposition coordinates of a marker is acquired as marker information, andthe avoidance operation is performed by calculating a distance from thework vehicle to the virtual line and a time until the work vehiclereaches the virtual line by using the marker position information andself-position information and orientation information of the workvehicle.

Since the system configuration and the configuration of the autonomouswork machine are similar to those described in the first embodiment, thedescription thereof will be omitted.

<Processing>

Next, a procedure of processing performed by the work vehicle 10according to the present embodiment will be described with reference toflowcharts of FIGS. 8A and 8B. The work vehicle 10 according to thepresent embodiment sets a virtual line between markers and performscontrol so that the work vehicle 10 does not deviate to a region beyondthe virtual line. Steps of performing the same processes as those in theflowcharts of FIGS. 5A and 5B are denoted by the same referencenumerals. Hereinafter, differences from FIGS. 5A and 5B will be mainlydescribed.

In step S801, the CPU 44 a acquires information on the self-position andorientation using the GPS sensor 48 and the orientation sensor 46.

In step S802, the CPU 44 a acquires marker position information(position coordinates) of the detected marker as marker information. Forexample, as described with reference to FIG. 4D in the first embodiment,the marker position information is stored in advance in the memory 44 cas map information so that the marker position information can bereferred to. The work vehicle 10 recognizes its self-position andorientation using the GPS sensor 48 and the orientation sensor 46,specifies which marker included in the map information is the markerdetected from the image captured by the camera unit 11, and acquiresmarker position information of the detected marker.

Alternatively, the marker position information can be specified from thelandscape information of the image captured by the camera unit 11. Forexample, landscape information and a marker included in an image arestored in advance in association with information of the distance to themarker obtained by measurement distance in the landscape. Then, whilethe work vehicle 10 is caused to travel in the work area, theassociation is performed at various places and stored as learninginformation. Then, by referring to this learning information, positioncoordinates of the marker detected from the image captured by the cameraunit 11 can be acquired as marker position information using theself-position and orientation recognized using the GPS sensor 48 and theorientation sensor 46.

Alternatively, the work vehicle 10 recognizes its self-position andorientation using the GPS sensor 48 and the orientation sensor 46, andacquires, on the basis of an image having parallax (S501 and S502),information on the distance (distance image) to a marker detected froman image captured by the camera unit 11. Furthermore, an angle (forexample, the angle α or the angle β in FIG. 6) at which the markerexists with respect to the photographing direction of the camera unit 11is obtained from the position of the marker with respect to the imagecenter of the captured image. Then, a direction in which the marker ispresent may be specified from the orientation of the work vehicle 10 andthe acquired angle, and position coordinates that is ahead along thedirection by a distance indicated by the acquired distance informationmay be acquired as the marker position information.

In step S803, the CPU 44 a determines whether or not two markersincluded in the plurality of markers are adjacent markers. Also in thepresent embodiment, the determination method is the same as that in thefirst embodiment, and thus detailed description thereof is omitted.

In step S804, the CPU 44 a calculates the distance from the work vehicle10 to a virtual line located ahead of the work vehicle 10 in thetraveling direction based on the traveling direction of the work vehicle10 and the virtual line located ahead in the traveling direction. In theexample of FIG. 4A, the distance to an intersection with the virtualline 411 located ahead in the traveling direction 402 is calculated.

Here, an example of a method of calculating the distance to theintersection with the virtual line 411 located ahead in the travelingdirection 402 of FIG. 4A will be described again with reference to FIG.6. In FIG. 6, a point O is a current position of the work vehicle 10. Apoint A corresponds to the marker 401 a in FIG. 4A, and a point Bcorresponds to the marker 401 b in FIG. 4A. When the distance to beobtained is X, X is the length of a line OC. Here, since the positioncoordinates of the point A, the position coordinates of the point B, andthe position coordinates (self-position) of the point O are known, thelength of the line OA and the length of the line OB can be obtained fromthese. Thereafter, the distance from the work vehicle 10 to the virtualline 411 located ahead in the traveling direction of the work vehicle 10is calculated by a procedure similar to the procedure described in thefirst embodiment.

Other steps are similar to the processing described with reference toFIGS. 5A and 5B.

As described above, in the second embodiment, marker positioninformation indicating position coordinates of a marker is acquired asmarker information, and the avoidance operation is performed bycalculating a distance from the work vehicle to the virtual line and atime until the work vehicle reaches the virtual line by using the markerposition information and self-position information and orientationinformation of the work vehicle.

As a result, the operation of the work vehicle can be controlled usingthe marker position information indicating the position coordinates ofthe marker and the self-position and orientation of the work vehicle.

Third Embodiment

In a third embodiment, an example will be described in which mapinformation including position information of markers arranged to definea work area is generated and presented to a user.

Since the system configuration and the configuration of the autonomouswork machine are similar to those described in the first embodiment, thedescription thereof will be omitted.

The work vehicle 10 acquires information on the distance to the detectedmarker from an image captured by the camera unit 11, while acquiringinformation on its self-position and orientation using the GPS sensor 48and the orientation sensor 46. As described in the first embodiment, thedistance to the marker can be acquired on the basis of an image havingparallax. Furthermore, an angle (for example, the angle α or the angle βin FIG. 6) at which the marker exists with respect to the photographingdirection of the camera unit 11 is obtained from the position of themarker with respect to the image center of the captured image asillustrated in FIG. 7. Then, a direction in which the marker is presentmay be specified from the orientation of the work vehicle 10 and theacquired angle, and position coordinates that is ahead along thedirection by a distance indicated by the acquired distance informationis acquired as the marker position information. Each time the workvehicle 10 detects a marker while performing work, the work vehiclecalculates position information (position coordinates) of the marker byusing information on the self-position and orientation, information onthe distance to the marker, and a direction in which the marker exists.Then, the calculated position information of the marker is plotted onthe map. As a result, map information including position information ofmarkers arranged to define a work area can be generated.

FIG. 9 is an example of a map on which position information of markersis plotted. Reference numeral 901 denoted a map, and the map is definedas a grid area divided in a grid pattern. Reference numerals 901 a to901 w are each position information of a plotted marker. The workvehicle 10 generates such map information and stores the map informationas a map database while performing work or traveling before startingwork. In addition, the generated map information may be presented to theuser. As a method of presentation to the user, when a display unit isprovided in the work vehicle 10, the presentation may be performed bydisplaying on the display unit. Alternatively, the work vehicle 10 maytransmit map information to a communication terminal (for example, atablet, a smartphone, or the like) possessed by the user and present themap information on a display screen of the communication terminal.

As described above, in the present embodiment, an example mapinformation including marker positions arranged to define a work area isgenerated and presented to the user. As a result, the user can acquirethe map information on manually arranged markers. Therefore, it is alsopossible to manually adjust the arrangement positions of the markerslater to redefine a more appropriate work area.

Note that the processing of the present embodiment may be performed inparallel with the first embodiment and the second embodiment, or may beperformed independently of these. In the case of performing theprocessing in parallel, at least one of the information of the virtualline acquired by the processing of the first embodiment or the secondembodiment and the position information of the marker acquired by theprocessing of the third embodiment may be reflected in the mapinformation and presented to the user.

In the embodiments described above, the lawn mower has been described asan example of the autonomous work machine, but the autonomous workmachine is not limited to the lawn mower. For example, the presentinvention can also be applied to other types of autonomous work machinessuch as an autonomous snow removing machines, golf ball collectors,outboard motors, and the like.

Summary of Embodiments

1. The autonomous work machine (for example, 10) of the embodimentsdescribed above is

an autonomous work machine that works in a work area, and includes

a detection means (for example, 11 and 44 a) that detects a plurality ofmarkers (for example, 401 a to 401 n) arranged to define the work area,

a specifying means (for example, 44 a) that specifies marker informationbased on a detection result of the detection means,

a setting means (for example, 44 a) that sets a virtual line (forexample, 411, 412, and 413) connecting the plurality of markers based onthe marker information specified by the specifying means, and

a control means (for example, 44 a) that controls the autonomous workmachine such that the autonomous work machine does not deviate to aregion beyond the virtual line set by the setting means.

According to this embodiment, it is possible to control a work machineusing markers that do not need to be individually distinguished. Forexample, the work machine can be controlled using the same type ofmarker.

2. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the control means calculates a time required for the autonomous workmachine to reach the virtual line, and controls the autonomous workmachine based on the calculated time.

According to this embodiment, the avoidance operation can be performedbefore the time required to reach the virtual line is reached. Inaddition, deviation can be prevented without using an IMU or a GPSsensor for recognizing the self-position.

3. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the control means calculates the time based on a speed of the autonomouswork machine and a distance from the autonomous work machine to thevirtual line.

According to this embodiment, the avoidance operation can be performedbefore the time required to reach the virtual line is reached. Inaddition, deviation can be prevented without using an IMU or a GPSsensor for recognizing the self-position.

4. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

a measuring means (for example, IMU or odometry) that measures a movingdistance of the autonomous work machine is further provided, and

the control means

calculates a distance from the autonomous work machine to the virtualline based on the marker information, and

controls the autonomous work machine based on the calculated distanceand the moving distance from a position of the autonomous work machinewhere the distance has been calculated.

According to this embodiment, even when a marker is no longer detectedon during the operation, the autonomous work machine can be controlled.

5. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the marker information includes distance information indicating adistance from the autonomous work machine to a marker, and

the setting means sets the virtual line based on the distanceinformation.

According to this embodiment, since a virtual line is set using distanceinformation indicating the distance to a marker, the virtual line can beset even if the position information of the marker is not known.

6. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the marker information includes marker position information indicating aposition coordinate of a marker, and

the setting means sets the virtual line based on the marker positioninformation.

According to this embodiment, since a virtual line is set using markerposition information, the virtual line can be set without additionallyacquiring information on the distance to a marker.

7. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

a storage means (for example, 44 c) that stores feature information of amarker is further provided, and

the specifying means specifies the marker information based on thefeature information of a marker stored in the storage means and afeature of a marker detected by the detection means.

According to this embodiment, it is possible to recognize a marker andacquire marker information for the marker.

8. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the control means stops, moves backward, or turns the autonomous workmachine in a case where a distance from the autonomous work machine tothe virtual line becomes equal to or less than a first threshold.

According to this embodiment, it is possible to prevent the autonomouswork machine from deviating to the region beyond the virtual line.

9. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the control means decelerates the autonomous work machine heading forthe virtual line in a case where the distance from the autonomous workmachine to the virtual line becomes equal to or less than a secondthreshold larger than the first threshold.

According to this embodiment, by decelerating in advance beforeperforming an operation of stop, backward movement, or turning, it ispossible to suppress sudden operation such as sudden stop, suddenbackward movement after sudden stop, or sudden turning.

10. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

an adjacent marker specifying means (for example, 44 a) that specifiestwo markers as adjacent markers among the plurality of markers detectedby the detection means is further provided, and

the control means sets a virtual line between the two markers specifiedas the adjacent markers by the adjacent marker specifying means.

According to this embodiment, since a virtual line is not set betweenmarkers that are not originally adjacent to each other, it is possibleto prevent the occurrence of a region where no work is performed.

11. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the adjacent marker specifying means specifies, as the adjacent markers,two markers having a distance therebetween within a predetermineddistance range among the plurality of markers.

According to this embodiment, it is possible to prevent markers having along distance from each other from being determined as adjacent markers.

12. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

in a case where another marker (for example, 451 c) detected by thedetection means is present in a region beyond a line connecting the twomarkers (for example, 451 b and 451 d), the adjacent marker specifyingmeans specifies that the two markers are not the adjacent markers.

According to this embodiment, since a virtual line is not set betweenmarkers that are not originally adjacent to each other, it is possibleto prevent the occurrence of a region where no work is performed.

13. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

each marker includes an indicator (for example, 431 and 432) indicatinga direction in which an adjacent marker is present, and

the adjacent marker specifying means specifies, as the adjacent marker,a second marker (for example, 431 or 432) present in a directionindicated by the indicator of a first marker (for example, 401 m).

According to this embodiment, it is possible to prevent a virtual linefrom being set between markers that are not originally adjacent to eachother.

14. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

an acquisition means that acquires trajectory information (for example,a trajectory along an arrow in FIG. 4C) of the autonomous work machineby causing the autonomous work machine to travel along markers that arearranged is further provided, and

the adjacent marker specifying means specifies, as the adjacent markers,two markers matching the trajectory information among the plurality ofmarkers.

According to this embodiment, it is possible to prevent a virtual linefrom being set between markers that do not match the trajectoryinformation and are not originally adjacent to each other.

15. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

an acquisition means that acquires boundary information (for example,475 and 476) of the work area designated on a map including the workarea is further provided, and

the adjacent marker specifying means specifies, as the adjacent markers,two markers matching the boundary information among the plurality ofmarkers.

According to this embodiment, it is possible to prevent a virtual linefrom being set between markers that do not match the boundaryinformation and are not originally adjacent to each other.

16. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the boundary information is arrangement information (for example, 476)of a plurality of markers arranged at a boundary of the work area, orinformation (for example, 475) of a boundary line indicating a boundaryof the work area.

According to this embodiment, it is possible to acquire arrangementinformation of markers designated on a map and information of boundarylines.

17. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the plurality of markers include a plurality of first type of markers(for example, 483) defining an outer edge of the work area, and aplurality of second type of markers (for example, 484) defining an innerregion that is included in an inside of the outer edge and excluded fromthe work area, and

the adjacent marker specifying means specifies the first type of markersand the second type of markers as not being the adjacent markers.

According to this embodiment, it is possible to prevent a virtual linefrom being set between a marker defining the outer edge and a markerdefining the inner region (island).

18. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the plurality of markers include a plurality of first type of markers(for example, 491 a to 491 e) arranged at first distance intervals, anda plurality of second type of markers (for example, 492 a to 492 f)arranged at second distance intervals smaller than the first distanceintervals, and

in a case where the second type of marker is present between two of thefirst type of markers among the plurality of first type of markers, theadjacent marker specifying means specifies the two of the first type ofmarkers as the adjacent markers.

According to this embodiment, it is possible to prevent the autonomouswork machine from deviating to the outside of the work area even in aregion having a complicated shape.

19. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

a route setting means that sets a travel route of the autonomous workmachine is further provided, and

the route setting means sets the travel route such that the virtual lineis not present on the travel route.

According to this embodiment, it is possible to prevent the autonomouswork machine from deviating to the outside of the work area in the casewhere it is necessary to travel to some predetermined position.

20. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the travel route is a travel route for returning to a station.

According to this embodiment, it is possible to prevent the autonomouswork machine from deviating to the outside of the work area when theautonomous work machine returns to the station.

21. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

a position specifying means (for example, 48) that specifies a currentposition of the autonomous work machine is further provided, and

the control means controls the autonomous work machine based oninformation on the virtual line and the current position of theautonomous work machine specified by the position specifying means.

According to this embodiment, it is possible to prevent the autonomouswork machine from deviating to the region beyond the virtual line.

22. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the control means reflects at least one of the marker positioninformation (for example, 901 a to 901 w) and the information on thevirtual line on the map information (for example, 900) of the work area.

According to this embodiment, it is possible to generate map informationreflecting marker position information and information on a virtualline.

23. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the control means presents, to a user, the map information on which atleast one of the marker position information and the information on thevirtual line is reflected.

According to this embodiment, the user can recognize the generated mapinformation.

24. In the autonomous work machine (for example, 10) of the embodimentsdescribed above,

the control means transmits, to a communication terminal (for example,470) of a user, the map information on which at least one of the markerposition information and the information on the virtual line isreflected.

According to this embodiment, it is possible to easily check thegenerated map information via the communication terminal held by theuser.

25. A control method for the autonomous work machine (for example, 10)of the embodiments described above is

a control method for an autonomous work machine that works in a workarea, and includes

a detection step for detecting a plurality of markers arranged to definethe work area,

a specifying step for specifying marker information based on a detectionresult of the detection step,

a setting step for setting a virtual line connecting the plurality ofmarkers based on the marker information specified in the specifyingstep, and

a control step for controlling the autonomous work machine such that theautonomous work machine does not deviate to a region beyond the virtualline set in the setting step.

According to this embodiment, it is possible to control a work machineusing markers that do not need to be individually distinguished. Forexample, the work machine can be controlled using the same type ofmarker.

26. A non-transitory computer readable storage medium storing a programaccording to the embodiment described above is

a storage medium storing a program for causing a computer to function asthe autonomous work machine according to the embodiments describedabove.

According to this embodiment, the autonomous work machine according tothe present invention can be realized by a computer.

According to the present invention, it is possible to control a workmachine using markers that do not need to be individually distinguished.

The present invention is not limited to the above-described embodiments,and various changes and modifications can be made without departing fromthe spirit and scope of the present invention. Therefore, in order tomake the scope of the present invention public, the following claims areattached.

What is claimed is:
 1. An autonomous work machine that works in a workarea, the autonomous work machine comprising: a detection unit thatdetects a plurality of markers arranged to define the work area; aspecifying unit that specifies marker information based on a detectionresult of the detection unit; a setting unit that sets a virtual lineconnecting the plurality of markers based on the marker informationspecified by the specifying unit; and a control unit that controls theautonomous work machine such that the autonomous work machine does notdeviate to a region beyond the virtual line set by the setting unit. 2.The autonomous work machine according to claim 1, wherein the controlunit calculates a time required for the autonomous work machine to reachthe virtual line, and controls the autonomous work machine based on thecalculated time.
 3. The autonomous work machine according to claim 2,wherein the control unit calculates the time based on a speed of theautonomous work machine and a distance from the autonomous work machineto the virtual line.
 4. The autonomous work machine according to claim1, further comprising a measuring unit that measures a moving distanceof the autonomous work machine, wherein the control unit calculates adistance from the autonomous work machine to the virtual line based onthe marker information, and controls the autonomous work machine basedon the calculated distance and the moving distance from a position ofthe autonomous work machine where the distance has been calculated. 5.The autonomous work machine according to claim 1, wherein the markerinformation includes distance information indicating a distance from theautonomous work machine to a marker, and the setting unit sets thevirtual line based on the distance information.
 6. The autonomous workmachine according to claim 1, wherein the marker information includesmarker position information indicating a position coordinate of amarker, and the setting unit sets the virtual line based on the markerposition information.
 7. The autonomous work machine according to claim1, further comprising a storage unit that stores feature information ofa marker, wherein the specifying unit specifies the marker informationbased on the feature information of a marker stored in the storage unitand a feature of a marker detected by the detection unit.
 8. Theautonomous work machine according to claim 1, wherein the control unitstops, moves backward, or turns the autonomous work machine in a casewhere a distance from the autonomous work machine to the virtual linebecomes equal to or less than a first threshold.
 9. The autonomous workmachine according to claim 8, wherein the control unit decelerates theautonomous work machine heading for the virtual line in a case where thedistance from the autonomous work machine to the virtual line becomesequal to or less than a second threshold larger than the firstthreshold.
 10. The autonomous work machine according to claim 1, furthercomprising an adjacent marker specifying unit that specifies two markersas adjacent markers among the plurality of markers detected by thedetection unit, wherein the control unit sets a virtual line between thetwo markers specified as the adjacent markers by the adjacent markerspecifying unit.
 11. The autonomous work machine according to claim 10,wherein the adjacent marker specifying unit specifies, as the adjacentmarkers, two markers having a distance therebetween within apredetermined distance range among the plurality of markers.
 12. Theautonomous work machine according to claim 10, wherein in a case whereanother marker detected by the detection unit is present in a regionbeyond a line connecting the two markers, the adjacent marker specifyingunit specifies that the two markers are not the adjacent markers. 13.The autonomous work machine according to claim 10, wherein each markerincludes an indicator indicating a direction in which an adjacent markeris present, and the adjacent marker specifying unit specifies, as theadjacent marker, a second marker present in a direction indicated by theindicator of a first marker.
 14. The autonomous work machine accordingto claim 10, further comprising an acquisition unit that acquirestrajectory information of the autonomous work machine by causing theautonomous work machine to travel along markers that are arranged,wherein the adjacent marker specifying unit specifies, as the adjacentmarkers, two markers matching the trajectory information among theplurality of markers.
 15. The autonomous work machine according to claim10, further comprising an acquisition unit that acquires boundaryinformation of the work area designated on a map including the workarea, wherein the adjacent marker specifying unit specifies, as theadjacent markers, two markers matching the boundary information amongthe plurality of markers.
 16. The autonomous work machine according toclaim 15, wherein the boundary information is arrangement information ofa plurality of markers arranged at a boundary of the work area, orinformation of a boundary line indicating a boundary of the work area.17. The autonomous work machine according to claim 10, wherein theplurality of markers include a plurality of first type of markersdefining an outer edge of the work area, and a plurality of second typeof markers defining an inner region that is included in an inside of theouter edge and excluded from the work area, and the adjacent markerspecifying unit specifies the first type of markers and the second typeof markers as not being the adjacent markers.
 18. The autonomous workmachine according to claim 10, wherein the plurality of markers includea plurality of first type of markers arranged at first distanceintervals, and a plurality of second type of markers arranged at seconddistance intervals smaller than the first distance intervals, and in acase where the second type of marker is present between two of the firsttype of markers among the plurality of first type of markers, theadjacent marker specifying unit specifies the two of the first type ofmarkers as the adjacent markers.
 19. The autonomous work machineaccording to claim 1, further comprising a route setting unit that setsa travel route of the autonomous work machine, wherein the route settingunit sets the travel route such that the virtual line is not present onthe travel route.
 20. The autonomous work machine according to claim 19,wherein the travel route is a travel route for returning to a station.21. The autonomous work machine according to claim 1, further comprisinga position specifying unit that specifies a current position of theautonomous work machine, wherein the control unit controls theautonomous work machine based on information on the virtual line and thecurrent position of the autonomous work machine specified by theposition specifying unit.
 22. The autonomous work machine according toclaim 6, wherein the control unit reflects at least one of the markerposition information and the information on the virtual line on mapinformation of the work area.
 23. The autonomous work machine accordingto claim 22, wherein the control unit presents, to a user, the mapinformation on which at least one of the marker position information andthe information on the virtual line is reflected.
 24. The autonomouswork machine according to claim 22, wherein the control unit transmits,to a communication terminal of a user, the map information on which atleast one of the marker position information and the information on thevirtual line is reflected.
 25. A control method for an autonomous workmachine that works in a work area, the control method comprising:detecting a plurality of markers arranged to define the work area;specifying marker information based on a detection result in thedetecting; setting a virtual line connecting the plurality of markersbased on the marker information specified in the specifying; andcontrolling the autonomous work machine such that the autonomous workmachine does not deviate to a region beyond the virtual line set in thesetting.
 26. A non-transitory computer readable storage medium storing aprogram for causing a computer to execute a control method for anautonomous work machine that works in a work area, the control methodcomprising: detecting a plurality of markers arranged to define the workarea; specifying marker information based on a detection result in thedetecting; setting a virtual line connecting the plurality of markersbased on the marker information specified in the specifying; andcontrolling the autonomous work machine such that the autonomous workmachine does not deviate to a region beyond the virtual line set in thesetting.